1. Field of the Invention
The present invention relates to an endoscope apparatus that reliably removes adherent substances from a surface of an observation window and thereby improves observability.
2. Description of the Related Art
In recent years, surgery using an endoscope aiming at minimally invasive medical treatment is becoming increasingly common. A challenge to such surgery under endoscopy is how to prevent deterioration of an observation environment due to adhesion of dirt to or fogging on an observation window disposed at a distal end portion of the endoscope.
Endoscopes for digestive organs remove fogging and dirt by supplying water to a lens at the distal end portion of the endoscope. In the case of transnasal endoscopes in particular, there may be cases where water droplets are not effectively removed after a water supply or air supply. Furthermore, in the case of endoscopes for surgery, there may be cases where adhered dirt consists of scattered blood, fat or the like resulting from surgery, which cannot be removed simply by supplying water.
As a solution for this problem, for example, a technique disclosed in Japanese Patent Application Laid-Open Publication No. 2009-254571 is known.
This conventional endoscope apparatus is provided with a transparent member provided opposed to an image pickup optical system at the distal end of an insertion portion, a transducer attached to the inner surface of the transparent member and a diffraction grating provided on the outer surface of the transparent member for converting ultrasound vibration from the transducer to a surface acoustic wave that propagates on the outer surface of the transparent member. The transducer attached to the inner surface of the transparent member and the diffraction grating on the outer surface of the transparent member are provided in the vicinity of the outer circumference of the transparent member so as not to block the field of view of the image pickup optical system.
Ultrasound vibration radiated from the transducer is converted to a surface acoustic wave by the diffraction grating on the outer surface of the transparent member and radiated in the direction of a grating vector of the diffraction grating. Here, the grating vector of the diffraction grating is defined as a direction of periodicity of the diffraction grating. The surface acoustic wave radiated from the diffraction grating propagates from the vicinity of the outer circumference of the transparent member in the direction of the observation field of view of the image pickup optical system in the center of the transparent member, acts on the water or dirt that blocks the visibility within the observation field of view and removes the water or dirt from the observation field of view.